[PATCH 10/10] simple-ipc: add Unix domain socket implementation
From: Jeff Hostetler <jeffhost@microsoft.com>
Create Unix domain socket based implementation of "simple-ipc".
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
---
Makefile | 2 +
compat/simple-ipc/ipc-unix-socket.c | 1093 +++++++++++++++++++++++++++
contrib/buildsystems/CMakeLists.txt | 2 +
simple-ipc.h | 7 +-
4 files changed, 1103 insertions(+), 1 deletion(-)
create mode 100644 compat/simple-ipc/ipc-unix-socket.c
diff --git a/Makefile b/Makefile
index e7ba8853ea6..f2524c02ff0 100644
--- a/Makefile
+++ b/Makefile
@@ -1681,6 +1681,8 @@ ifdef NO_UNIX_SOCKETS
BASIC_CFLAGS += -DNO_UNIX_SOCKETS
else
LIB_OBJS += unix-socket.o
+ LIB_OBJS += compat/simple-ipc/ipc-shared.o
+ LIB_OBJS += compat/simple-ipc/ipc-unix-socket.o
endif
ifdef USE_WIN32_IPC
diff --git a/compat/simple-ipc/ipc-unix-socket.c b/compat/simple-ipc/ipc-unix-socket.c
new file mode 100644
index 00000000000..be100049e4b
--- /dev/null
+++ b/compat/simple-ipc/ipc-unix-socket.c
@@ -0,0 +1,1093 @@
+#include "cache.h"
+#include "simple-ipc.h"
+#include "strbuf.h"
+#include "pkt-line.h"
+#include "thread-utils.h"
+#include "unix-socket.h"
+
+#ifdef NO_UNIX_SOCKETS
+#error compat/simple-ipc/ipc-unix-socket.c requires Unix sockets
+#endif
+
+enum ipc_active_state ipc_get_active_state(const char *path)
+{
+ enum ipc_active_state state = IPC_STATE__OTHER_ERROR;
+ struct ipc_client_connect_options options
+ = IPC_CLIENT_CONNECT_OPTIONS_INIT;
+ struct stat st;
+ int fd_test = -1;
+
+ options.wait_if_busy = 0;
+ options.wait_if_not_found = 0;
+
+ if (lstat(path, &st) == -1) {
+ switch (errno) {
+ case ENOENT:
+ case ENOTDIR:
+ return IPC_STATE__NOT_LISTENING;
+ default:
+ return IPC_STATE__INVALID_PATH;
+ }
+ }
+
+ /* also complain if a plain file is in the way */
+ if ((st.st_mode & S_IFMT) != S_IFSOCK)
+ return IPC_STATE__INVALID_PATH;
+
+ /*
+ * Just because the filesystem has a S_IFSOCK type inode
+ * at `path`, doesn't mean it that there is a server listening.
+ * Ping it to be sure.
+ */
+ state = ipc_client_try_connect(path, &options, &fd_test);
+ close(fd_test);
+
+ return state;
+}
+
+/*
+ * This value was chosen at random.
+ */
+#define WAIT_STEP_MS (50)
+
+/*
+ * Try to connect to the server. If the server is just starting up or
+ * is very busy, we may not get a connection the first time.
+ */
+static enum ipc_active_state connect_to_server(
+ const char *path,
+ int timeout_ms,
+ const struct ipc_client_connect_options *options,
+ int *pfd)
+{
+ int wait_ms = 50;
+ int k;
+
+ *pfd = -1;
+
+ for (k = 0; k < timeout_ms; k += wait_ms) {
+ int fd = unix_stream_connect(path);
+
+ if (fd != -1) {
+ *pfd = fd;
+ return IPC_STATE__LISTENING;
+ }
+
+ if (errno == ENOENT) {
+ if (!options->wait_if_not_found)
+ return IPC_STATE__PATH_NOT_FOUND;
+
+ goto sleep_and_try_again;
+ }
+
+ if (errno == ETIMEDOUT) {
+ if (!options->wait_if_busy)
+ return IPC_STATE__NOT_LISTENING;
+
+ goto sleep_and_try_again;
+ }
+
+ if (errno == ECONNREFUSED) {
+ if (!options->wait_if_busy)
+ return IPC_STATE__NOT_LISTENING;
+
+ goto sleep_and_try_again;
+ }
+
+ return IPC_STATE__OTHER_ERROR;
+
+ sleep_and_try_again:
+ sleep_millisec(wait_ms);
+ }
+
+ return IPC_STATE__NOT_LISTENING;
+}
+
+/*
+ * A randomly chosen timeout value.
+ */
+#define MY_CONNECTION_TIMEOUT_MS (1000)
+
+enum ipc_active_state ipc_client_try_connect(
+ const char *path,
+ const struct ipc_client_connect_options *options,
+ int *pfd)
+{
+ enum ipc_active_state state = IPC_STATE__OTHER_ERROR;
+
+ *pfd = -1;
+
+ trace2_region_enter("ipc-client", "try-connect", NULL);
+ trace2_data_string("ipc-client", NULL, "try-connect/path", path);
+
+ state = connect_to_server(path, MY_CONNECTION_TIMEOUT_MS,
+ options, pfd);
+
+ trace2_data_intmax("ipc-client", NULL, "try-connect/state",
+ (intmax_t)state);
+ trace2_region_leave("ipc-client", "try-connect", NULL);
+ return state;
+}
+
+int ipc_client_send_command_to_fd(int fd, const char *message,
+ struct strbuf *answer)
+{
+ int ret = 0;
+
+ strbuf_setlen(answer, 0);
+
+ trace2_region_enter("ipc-client", "send-command", NULL);
+
+ if (write_packetized_from_buf(message, strlen(message), fd, 1) < 0) {
+ ret = error(_("could not send IPC command"));
+ goto done;
+ }
+
+ if (read_packetized_to_strbuf(fd, answer, PACKET_READ_NEVER_DIE) < 0) {
+ ret = error(_("could not read IPC response"));
+ goto done;
+ }
+
+done:
+ trace2_region_leave("ipc-client", "send-command", NULL);
+ return ret;
+}
+
+int ipc_client_send_command(const char *path,
+ const struct ipc_client_connect_options *options,
+ const char *message, struct strbuf *answer)
+{
+ int fd;
+ int ret = -1;
+ enum ipc_active_state state;
+
+ state = ipc_client_try_connect(path, options, &fd);
+
+ if (state != IPC_STATE__LISTENING)
+ return ret;
+
+ ret = ipc_client_send_command_to_fd(fd, message, answer);
+ close(fd);
+ return ret;
+}
+
+static int set_socket_blocking_flag(int fd, int make_nonblocking)
+{
+ int flags;
+
+ flags = fcntl(fd, F_GETFL, NULL);
+
+ if (flags < 0)
+ return -1;
+
+ if (make_nonblocking)
+ flags |= O_NONBLOCK;
+ else
+ flags &= ~O_NONBLOCK;
+
+ return fcntl(fd, F_SETFL, flags);
+}
+
+/*
+ * Magic numbers used to annotate callback instance data.
+ * These are used to help guard against accidentally passing the
+ * wrong instance data across multiple levels of callbacks (which
+ * is easy to do if there are `void*` arguments).
+ */
+enum magic {
+ MAGIC_SERVER_REPLY_DATA,
+ MAGIC_WORKER_THREAD_DATA,
+ MAGIC_ACCEPT_THREAD_DATA,
+ MAGIC_SERVER_DATA,
+};
+
+struct ipc_server_reply_data {
+ enum magic magic;
+ int fd;
+ struct ipc_worker_thread_data *worker_thread_data;
+};
+
+struct ipc_worker_thread_data {
+ enum magic magic;
+ struct ipc_worker_thread_data *next_thread;
+ struct ipc_server_data *server_data;
+ pthread_t pthread_id;
+};
+
+struct ipc_accept_thread_data {
+ enum magic magic;
+ struct ipc_server_data *server_data;
+ int fd_listen;
+ ino_t inode_listen;
+ int fd_send_shutdown;
+ int fd_wait_shutdown;
+ pthread_t pthread_id;
+};
+
+/*
+ * With unix-sockets, the conceptual "ipc-server" is implemented as a single
+ * controller "accept-thread" thread and a pool of "worker-thread" threads.
+ * The former does the usual `accept()` loop and dispatches connections
+ * to an idle worker thread. The worker threads wait in an idle loop for
+ * a new connection, communicate with the client and relay data to/from
+ * the `application_cb` and then wait for another connection from the
+ * server thread. This avoids the overhead of constantly creating and
+ * destroying threads.
+ */
+struct ipc_server_data {
+ enum magic magic;
+ ipc_server_application_cb *application_cb;
+ void *application_data;
+ struct strbuf buf_path;
+
+ struct ipc_accept_thread_data *accept_thread;
+ struct ipc_worker_thread_data *worker_thread_list;
+
+ pthread_mutex_t work_available_mutex;
+ pthread_cond_t work_available_cond;
+
+ /*
+ * Accepted but not yet processed client connections are kept
+ * in a circular buffer FIFO. The queue is empty when the
+ * positions are equal.
+ */
+ int *fifo_fds;
+ int queue_size;
+ int back_pos;
+ int front_pos;
+
+ int shutdown_requested;
+ int is_stopped;
+};
+
+/*
+ * Remove and return the oldest queued connection.
+ *
+ * Returns -1 if empty.
+ */
+static int fifo_dequeue(struct ipc_server_data *server_data)
+{
+ /* ASSERT holding mutex */
+
+ int fd;
+
+ if (server_data->back_pos == server_data->front_pos)
+ return -1;
+
+ fd = server_data->fifo_fds[server_data->front_pos];
+ server_data->fifo_fds[server_data->front_pos] = -1;
+
+ server_data->front_pos++;
+ if (server_data->front_pos == server_data->queue_size)
+ server_data->front_pos = 0;
+
+ return fd;
+}
+
+/*
+ * Push a new fd onto the back of the queue.
+ *
+ * Drop it and return -1 if queue is already full.
+ */
+static int fifo_enqueue(struct ipc_server_data *server_data, int fd)
+{
+ /* ASSERT holding mutex */
+
+ int next_back_pos;
+
+ next_back_pos = server_data->back_pos + 1;
+ if (next_back_pos == server_data->queue_size)
+ next_back_pos = 0;
+
+ if (next_back_pos == server_data->front_pos) {
+ /* Queue is full. Just drop it. */
+ close(fd);
+ return -1;
+ }
+
+ server_data->fifo_fds[server_data->back_pos] = fd;
+ server_data->back_pos = next_back_pos;
+
+ return fd;
+}
+
+/*
+ * Wait for a connection to be queued to the FIFO and return it.
+ *
+ * Returns -1 if someone has already requested a shutdown.
+ */
+static int worker_thread__wait_for_connection(
+ struct ipc_worker_thread_data *worker_thread_data)
+{
+ /* ASSERT NOT holding mutex */
+
+ struct ipc_server_data *server_data = worker_thread_data->server_data;
+ int fd = -1;
+
+ pthread_mutex_lock(&server_data->work_available_mutex);
+ for (;;) {
+ if (server_data->shutdown_requested)
+ break;
+
+ fd = fifo_dequeue(server_data);
+ if (fd >= 0)
+ break;
+
+ pthread_cond_wait(&server_data->work_available_cond,
+ &server_data->work_available_mutex);
+ }
+ pthread_mutex_unlock(&server_data->work_available_mutex);
+
+ return fd;
+}
+
+/*
+ * Forward declare our reply callback function so that any compiler
+ * errors are reported when we actually define the function (in addition
+ * to any errors reported when we try to pass this callback function as
+ * a parameter in a function call). The former are easier to understand.
+ */
+static ipc_server_reply_cb do_io_reply_callback;
+
+/*
+ * Relay application's response message to the client process.
+ * (We do not flush at this point because we allow the caller
+ * to chunk data to the client thru us.)
+ */
+static int do_io_reply_callback(struct ipc_server_reply_data *reply_data,
+ const char *response, size_t response_len)
+{
+ if (reply_data->magic != MAGIC_SERVER_REPLY_DATA)
+ BUG("reply_cb called with wrong instance data");
+
+ return write_packetized_from_buf(response, response_len,
+ reply_data->fd, 0);
+}
+
+/* A randomly chosen value. */
+#define MY_WAIT_POLL_TIMEOUT_MS (10)
+
+/*
+ * If the client hangs up without sending any data on the wire, just
+ * quietly close the socket and ignore this client.
+ *
+ * This worker thread is committed to reading the IPC request data
+ * from the client at the other end of this fd. Wait here for the
+ * client to actually put something on the wire -- because if the
+ * client just does a ping (connect and hangup without sending any
+ * data), our use of the pkt-line read routines will spew an error
+ * message.
+ *
+ * Return -1 if the client hung up.
+ * Return 0 if data (possibly incomplete) is ready.
+ */
+static int worker_thread__wait_for_io_start(
+ struct ipc_worker_thread_data *worker_thread_data,
+ int fd)
+{
+ struct ipc_server_data *server_data = worker_thread_data->server_data;
+ struct pollfd pollfd[1];
+ int result;
+
+ for (;;) {
+ pollfd[0].fd = fd;
+ pollfd[0].events = POLLIN;
+
+ result = poll(pollfd, 1, MY_WAIT_POLL_TIMEOUT_MS);
+ if (result < 0) {
+ if (errno == EINTR)
+ continue;
+ goto cleanup;
+ }
+
+ if (result == 0) {
+ /* a timeout */
+
+ int in_shutdown;
+
+ pthread_mutex_lock(&server_data->work_available_mutex);
+ in_shutdown = server_data->shutdown_requested;
+ pthread_mutex_unlock(&server_data->work_available_mutex);
+
+ /*
+ * If a shutdown is already in progress and this
+ * client has not started talking yet, just drop it.
+ */
+ if (in_shutdown)
+ goto cleanup;
+ continue;
+ }
+
+ if (pollfd[0].revents & POLLHUP)
+ goto cleanup;
+
+ if (pollfd[0].revents & POLLIN)
+ return 0;
+
+ goto cleanup;
+ }
+
+cleanup:
+ close(fd);
+ return -1;
+}
+
+/*
+ * Receive the request/command from the client and pass it to the
+ * registered request-callback. The request-callback will compose
+ * a response and call our reply-callback to send it to the client.
+ */
+static int worker_thread__do_io(
+ struct ipc_worker_thread_data *worker_thread_data,
+ int fd)
+{
+ /* ASSERT NOT holding lock */
+
+ struct strbuf buf = STRBUF_INIT;
+ struct ipc_server_reply_data reply_data;
+ int ret = 0;
+
+ reply_data.magic = MAGIC_SERVER_REPLY_DATA;
+ reply_data.worker_thread_data = worker_thread_data;
+
+ reply_data.fd = fd;
+
+ ret = read_packetized_to_strbuf(reply_data.fd, &buf,
+ PACKET_READ_NEVER_DIE);
+ if (ret >= 0) {
+ ret = worker_thread_data->server_data->application_cb(
+ worker_thread_data->server_data->application_data,
+ buf.buf, do_io_reply_callback, &reply_data);
+
+ packet_flush_gently(reply_data.fd);
+ }
+ else {
+ /*
+ * The client probably disconnected/shutdown before it
+ * could send a well-formed message. Ignore it.
+ */
+ }
+
+ strbuf_release(&buf);
+ close(reply_data.fd);
+
+ return ret;
+}
+
+/*
+ * Block SIGPIPE on the current thread (so that we get EPIPE from
+ * write() rather than an actual signal).
+ *
+ * Note that using sigchain_push() and _pop() to control SIGPIPE
+ * around our IO calls is not thread safe:
+ * [] It uses a global stack of handler frames.
+ * [] It uses ALLOC_GROW() to resize it.
+ * [] Finally, according to the `signal(2)` man-page:
+ * "The effects of `signal()` in a multithreaded process are unspecified."
+ */
+static void thread_block_sigpipe(sigset_t *old_set)
+{
+ sigset_t new_set;
+
+ sigemptyset(&new_set);
+ sigaddset(&new_set, SIGPIPE);
+
+ sigemptyset(old_set);
+ pthread_sigmask(SIG_BLOCK, &new_set, old_set);
+}
+
+/*
+ * Thread proc for an IPC worker thread. It handles a series of
+ * connections from clients. It pulls the next fd from the queue
+ * processes it, and then waits for the next client.
+ *
+ * Block SIGPIPE in this worker thread for the life of the thread.
+ * This avoids stray (and sometimes delayed) SIGPIPE signals caused
+ * by client errors and/or when we are under extremely heavy IO load.
+ *
+ * This means that the application callback will have SIGPIPE blocked.
+ * The callback should not change it.
+ */
+static void *worker_thread_proc(void *_worker_thread_data)
+{
+ struct ipc_worker_thread_data *worker_thread_data = _worker_thread_data;
+ struct ipc_server_data *server_data = worker_thread_data->server_data;
+ sigset_t old_set;
+ int fd, io;
+ int ret;
+
+ trace2_thread_start("ipc-worker");
+
+ thread_block_sigpipe(&old_set);
+
+ for (;;) {
+ fd = worker_thread__wait_for_connection(worker_thread_data);
+ if (fd == -1)
+ break; /* in shutdown */
+
+ io = worker_thread__wait_for_io_start(worker_thread_data, fd);
+ if (io == -1)
+ continue; /* client hung up without sending anything */
+
+ ret = worker_thread__do_io(worker_thread_data, fd);
+
+ if (ret == SIMPLE_IPC_QUIT) {
+ trace2_data_string("ipc-worker", NULL, "queue_stop_async",
+ "application_quit");
+ /* The application told us to shutdown. */
+ ipc_server_stop_async(server_data);
+ break;
+ }
+ }
+
+ trace2_thread_exit();
+ return NULL;
+}
+
+/*
+ * Return 1 if someone deleted or stole the on-disk socket from us.
+ */
+static int socket_was_stolen(struct ipc_accept_thread_data *accept_thread_data)
+{
+ struct stat st;
+
+ if (lstat(accept_thread_data->server_data->buf_path.buf, &st) == -1)
+ return 1;
+
+ if (st.st_ino != accept_thread_data->inode_listen)
+ return 1;
+
+ return 0;
+}
+
+/* A randomly chosen value. */
+#define MY_ACCEPT_POLL_TIMEOUT_MS (60 * 1000)
+
+/*
+ * Accept a new client connection on our socket. This uses non-blocking
+ * IO so that we can also wait for shutdown requests on our socket-pair
+ * without actually spinning on a fast timeout.
+ */
+static int accept_thread__wait_for_connection(
+ struct ipc_accept_thread_data *accept_thread_data)
+{
+ struct pollfd pollfd[2];
+ int result;
+
+ for (;;) {
+ pollfd[0].fd = accept_thread_data->fd_wait_shutdown;
+ pollfd[0].events = POLLIN;
+
+ pollfd[1].fd = accept_thread_data->fd_listen;
+ pollfd[1].events = POLLIN;
+
+ result = poll(pollfd, 2, MY_ACCEPT_POLL_TIMEOUT_MS);
+ if (result < 0) {
+ if (errno == EINTR)
+ continue;
+ return result;
+ }
+
+ if (result == 0) {
+ /* a timeout */
+
+ /*
+ * If someone deletes or force-creates a new unix
+ * domain socket at out path, all future clients
+ * will be routed elsewhere and we silently starve.
+ * If that happens, just queue a shutdown.
+ */
+ if (socket_was_stolen(
+ accept_thread_data)) {
+ trace2_data_string("ipc-accept", NULL,
+ "queue_stop_async",
+ "socket_stolen");
+ ipc_server_stop_async(
+ accept_thread_data->server_data);
+ }
+ continue;
+ }
+
+ if (pollfd[0].revents & POLLIN) {
+ /* shutdown message queued to socketpair */
+ return -1;
+ }
+
+ if (pollfd[1].revents & POLLIN) {
+ /* a connection is available on fd_listen */
+
+ int client_fd = accept(accept_thread_data->fd_listen,
+ NULL, NULL);
+ if (client_fd >= 0)
+ return client_fd;
+
+ /*
+ * An error here is unlikely -- it probably
+ * indicates that the connecting process has
+ * already dropped the connection.
+ */
+ continue;
+ }
+
+ BUG("unandled poll result errno=%d r[0]=%d r[1]=%d",
+ errno, pollfd[0].revents, pollfd[1].revents);
+ }
+}
+
+/*
+ * Thread proc for the IPC server "accept thread". This waits for
+ * an incoming socket connection, appends it to the queue of available
+ * connections, and notifies a worker thread to process it.
+ *
+ * Block SIGPIPE in this thread for the life of the thread. This
+ * avoids any stray SIGPIPE signals when closing pipe fds under
+ * extremely heavy loads (such as when the fifo queue is full and we
+ * drop incomming connections).
+ */
+static void *accept_thread_proc(void *_accept_thread_data)
+{
+ struct ipc_accept_thread_data *accept_thread_data = _accept_thread_data;
+ struct ipc_server_data *server_data = accept_thread_data->server_data;
+ sigset_t old_set;
+
+ trace2_thread_start("ipc-accept");
+
+ thread_block_sigpipe(&old_set);
+
+ for (;;) {
+ int client_fd = accept_thread__wait_for_connection(
+ accept_thread_data);
+
+ pthread_mutex_lock(&server_data->work_available_mutex);
+ if (server_data->shutdown_requested) {
+ pthread_mutex_unlock(&server_data->work_available_mutex);
+ if (client_fd >= 0)
+ close(client_fd);
+ break;
+ }
+
+ if (client_fd < 0) {
+ /* ignore transient accept() errors */
+ }
+ else {
+ fifo_enqueue(server_data, client_fd);
+ pthread_cond_broadcast(&server_data->work_available_cond);
+ }
+ pthread_mutex_unlock(&server_data->work_available_mutex);
+ }
+
+ trace2_thread_exit();
+ return NULL;
+}
+
+/*
+ * We can't predict the connection arrival rate relative to the worker
+ * processing rate, therefore we allow the "accept-thread" to queue up
+ * a generous number of connections, since we'd rather have the client
+ * not unnecessarily timeout if we can avoid it. (The assumption is
+ * that this will be used for FSMonitor and a few second wait on a
+ * connection is better than having the client timeout and do the full
+ * computation itself.)
+ *
+ * The FIFO queue size is set to a multiple of the worker pool size.
+ * This value chosen at random.
+ */
+#define FIFO_SCALE (100)
+
+/*
+ * The backlog value for `listen(2)`. This doesn't need to huge,
+ * rather just large enough for our "accept-thread" to wake up and
+ * queue incoming connections onto the FIFO without the kernel
+ * dropping any.
+ *
+ * This value chosen at random.
+ */
+#define LISTEN_BACKLOG (50)
+
+/*
+ * Create a unix domain socket at the given path to listen for
+ * client connections. The resulting socket will then appear
+ * in the filesystem as an inode with S_IFSOCK. The inode is
+ * itself created as part of the `bind(2)` operation.
+ *
+ * The term "socket" is ambiguous in this context. We want to open a
+ * "socket-fd" that is bound to a "socket-inode" (path) on disk. We
+ * listen on "socket-fd" for new connections and clients try to
+ * open/connect using the "socket-inode" pathname.
+ *
+ * Unix domain sockets have a fundamental design flaw because the
+ * "socket-inode" persists until the pathname is deleted; closing the listening
+ * "socket-fd" only closes the socket handle/descriptor, it does not delete
+ * the inode/pathname.
+ *
+ * Well-behaving service daemons are expected to also delete the inode
+ * before shutdown. If a service crashes (or forgets) it can leave
+ * the (now stale) inode in the filesystem. This behaves like a stale
+ * ".lock" file and may prevent future service instances from starting
+ * up correctly. (Because they won't be able to bind.)
+ *
+ * When future service instances try to create the listener socket,
+ * `bind(2)` will fail with EADDRINUSE -- because the inode already
+ * exists. However, the new instance cannot tell if it is a stale
+ * inode *or* another service instance is already running.
+ *
+ * One possible solution is to blindly unlink the inode before
+ * attempting to bind a new socket-fd (and thus create) a new
+ * socket-inode. Then `bind(2)` should always succeed. However, if
+ * there is an existing service instance, it would be orphaned --
+ * it would still be listening on a socket-fd that is still bound
+ * to an (unlinked) socket-inode, but that socket-inode is no longer
+ * associated with the pathname. New client connections will arrive
+ * at our new socket-inode and not the existing server's. (It is upto
+ * the existing server to detect that its socket-inode has been
+ * stolen and shutdown.)
+ *
+ * Since this is rather obscure and infrequent, we try to "gently"
+ * create the socket-inode without disturbing an existing service.
+ */
+static int create_listener_socket(const char *path,
+ const struct ipc_server_opts *ipc_opts)
+{
+ int fd_listen;
+ int fd_client;
+ struct unix_stream_listen_opts uslg_opts = {
+ .listen_backlog_size = LISTEN_BACKLOG,
+ .force_unlink_before_bind = 0,
+ .disallow_chdir = ipc_opts->uds_disallow_chdir
+ };
+
+ trace2_data_string("ipc-server", NULL, "try-listen-gently", path);
+
+ /*
+ * Assume socket-inode does not exist and try to (gently)
+ * create a new socket-inode on disk at pathname and bind
+ * socket-fd to it.
+ */
+ fd_listen = unix_stream_listen_gently(path, &uslg_opts);
+ if (fd_listen >= 0)
+ return fd_listen;
+
+ if (errno != EADDRINUSE)
+ return error_errno(_("could not create socket '%s'"),
+ path);
+
+ trace2_data_string("ipc-server", NULL, "try-detect-server", path);
+
+ /*
+ * A socket-inode at pathname exists on disk, but we don't
+ * know if it a server is using it or if it is a stale inode.
+ *
+ * poke it with a trivial connection to try to find out.
+ */
+ fd_client = unix_stream_connect(path);
+ if (fd_client >= 0) {
+ /*
+ * An existing service process is alive and accepted our
+ * connection.
+ */
+ close(fd_client);
+
+ /*
+ * We cannot create a new socket-inode here, so we cannot
+ * startup a new server on this pathname.
+ */
+ errno = EADDRINUSE;
+ return error_errno(_("socket already in use '%s'"),
+ path);
+ }
+
+ trace2_data_string("ipc-server", NULL, "try-listen-force", path);
+
+ /*
+ * A socket-inode at pathname exists on disk, but we were not
+ * able to connect to it, so we believe that this is a stale
+ * socket-inode that a previous server forgot to delete. Use
+ * the tradional solution: force unlink it and create a new
+ * one.
+ *
+ * TODO Note that it is possible that another server is
+ * listening, but is either just starting up and not yet
+ * responsive or is stuck somehow. For now, I'm OK with
+ * stealing the socket-inode from it in this case.
+ */
+ uslg_opts.force_unlink_before_bind = 1;
+ fd_listen = unix_stream_listen_gently(path, &uslg_opts);
+ if (fd_listen >= 0)
+ return fd_listen;
+
+ return error_errno(_("could not force create socket '%s'"), path);
+}
+
+static int setup_listener_socket(const char *path, ino_t *inode,
+ const struct ipc_server_opts *ipc_opts)
+{
+ int fd_listen;
+ struct stat st;
+
+ trace2_region_enter("ipc-server", "create-listener_socket", NULL);
+ fd_listen = create_listener_socket(path, ipc_opts);
+ trace2_region_leave("ipc-server", "create-listener_socket", NULL);
+
+ if (fd_listen < 0)
+ return fd_listen;
+
+ /*
+ * We just bound a socket (descriptor) to a newly created unix
+ * domain socket in the filesystem. Capture the inode number
+ * so we can later detect if/when someone else force-creates a
+ * new socket and effectively steals the path from us. (Which
+ * would leave us listening to a socket that no client could
+ * reach.)
+ */
+ if (lstat(path, &st) < 0) {
+ int saved_errno = errno;
+
+ close(fd_listen);
+ unlink(path);
+
+ errno = saved_errno;
+ return error_errno(_("could not lstat listener socket '%s'"),
+ path);
+ }
+
+ if (set_socket_blocking_flag(fd_listen, 1)) {
+ int saved_errno = errno;
+
+ close(fd_listen);
+ unlink(path);
+
+ errno = saved_errno;
+ return error_errno(_("making listener socket nonblocking '%s'"),
+ path);
+ }
+
+ *inode = st.st_ino;
+
+ return fd_listen;
+}
+
+/*
+ * Start IPC server in a pool of background threads.
+ */
+int ipc_server_run_async(struct ipc_server_data **returned_server_data,
+ const char *path, const struct ipc_server_opts *opts,
+ ipc_server_application_cb *application_cb,
+ void *application_data)
+{
+ struct ipc_server_data *server_data;
+ int fd_listen;
+ ino_t inode_listen;
+ int sv[2];
+ int k;
+ int nr_threads = opts->nr_threads;
+
+ *returned_server_data = NULL;
+
+ /*
+ * Create a socketpair and set sv[1] to non-blocking. This
+ * will used to send a shutdown message to the accept-thread
+ * and allows the accept-thread to wait on EITHER a client
+ * connection or a shutdown request without spinning.
+ */
+ if (socketpair(AF_UNIX, SOCK_STREAM, 0, sv) < 0)
+ return error_errno(_("could not create socketpair for '%s'"),
+ path);
+
+ if (set_socket_blocking_flag(sv[1], 1)) {
+ int saved_errno = errno;
+ close(sv[0]);
+ close(sv[1]);
+ errno = saved_errno;
+ return error_errno(_("making socketpair nonblocking '%s'"),
+ path);
+ }
+
+ fd_listen = setup_listener_socket(path, &inode_listen, opts);
+ if (fd_listen < 0) {
+ int saved_errno = errno;
+ close(sv[0]);
+ close(sv[1]);
+ errno = saved_errno;
+ return -1;
+ }
+
+ server_data = xcalloc(1, sizeof(*server_data));
+ server_data->magic = MAGIC_SERVER_DATA;
+ server_data->application_cb = application_cb;
+ server_data->application_data = application_data;
+ strbuf_init(&server_data->buf_path, 0);
+ strbuf_addstr(&server_data->buf_path, path);
+
+ if (nr_threads < 1)
+ nr_threads = 1;
+
+ pthread_mutex_init(&server_data->work_available_mutex, NULL);
+ pthread_cond_init(&server_data->work_available_cond, NULL);
+
+ server_data->queue_size = nr_threads * FIFO_SCALE;
+ server_data->fifo_fds = xcalloc(server_data->queue_size,
+ sizeof(*server_data->fifo_fds));
+
+ server_data->accept_thread =
+ xcalloc(1, sizeof(*server_data->accept_thread));
+ server_data->accept_thread->magic = MAGIC_ACCEPT_THREAD_DATA;
+ server_data->accept_thread->server_data = server_data;
+ server_data->accept_thread->fd_listen = fd_listen;
+ server_data->accept_thread->inode_listen = inode_listen;
+ server_data->accept_thread->fd_send_shutdown = sv[0];
+ server_data->accept_thread->fd_wait_shutdown = sv[1];
+
+ if (pthread_create(&server_data->accept_thread->pthread_id, NULL,
+ accept_thread_proc, server_data->accept_thread))
+ die_errno(_("could not start accept_thread '%s'"), path);
+
+ for (k = 0; k < nr_threads; k++) {
+ struct ipc_worker_thread_data *wtd;
+
+ wtd = xcalloc(1, sizeof(*wtd));
+ wtd->magic = MAGIC_WORKER_THREAD_DATA;
+ wtd->server_data = server_data;
+
+ if (pthread_create(&wtd->pthread_id, NULL, worker_thread_proc,
+ wtd)) {
+ if (k == 0)
+ die(_("could not start worker[0] for '%s'"),
+ path);
+ /*
+ * Limp along with the thread pool that we have.
+ */
+ break;
+ }
+
+ wtd->next_thread = server_data->worker_thread_list;
+ server_data->worker_thread_list = wtd;
+ }
+
+ *returned_server_data = server_data;
+ return 0;
+}
+
+/*
+ * Gently tell the IPC server treads to shutdown.
+ * Can be run on any thread.
+ */
+int ipc_server_stop_async(struct ipc_server_data *server_data)
+{
+ /* ASSERT NOT holding mutex */
+
+ int fd;
+
+ if (!server_data)
+ return 0;
+
+ trace2_region_enter("ipc-server", "server-stop-async", NULL);
+
+ pthread_mutex_lock(&server_data->work_available_mutex);
+
+ server_data->shutdown_requested = 1;
+
+ /*
+ * Write a byte to the shutdown socket pair to wake up the
+ * accept-thread.
+ */
+ if (write(server_data->accept_thread->fd_send_shutdown, "Q", 1) < 0)
+ error_errno("could not write to fd_send_shutdown");
+
+ /*
+ * Drain the queue of existing connections.
+ */
+ while ((fd = fifo_dequeue(server_data)) != -1)
+ close(fd);
+
+ /*
+ * Gently tell worker threads to stop processing new connections
+ * and exit. (This does not abort in-process conversations.)
+ */
+ pthread_cond_broadcast(&server_data->work_available_cond);
+
+ pthread_mutex_unlock(&server_data->work_available_mutex);
+
+ trace2_region_leave("ipc-server", "server-stop-async", NULL);
+
+ return 0;
+}
+
+/*
+ * Wait for all IPC server threads to stop.
+ */
+int ipc_server_await(struct ipc_server_data *server_data)
+{
+ pthread_join(server_data->accept_thread->pthread_id, NULL);
+
+ if (!server_data->shutdown_requested)
+ BUG("ipc-server: accept-thread stopped for '%s'",
+ server_data->buf_path.buf);
+
+ while (server_data->worker_thread_list) {
+ struct ipc_worker_thread_data *wtd =
+ server_data->worker_thread_list;
+
+ pthread_join(wtd->pthread_id, NULL);
+
+ server_data->worker_thread_list = wtd->next_thread;
+ free(wtd);
+ }
+
+ server_data->is_stopped = 1;
+
+ return 0;
+}
+
+void ipc_server_free(struct ipc_server_data *server_data)
+{
+ struct ipc_accept_thread_data * accept_thread_data;
+
+ if (!server_data)
+ return;
+
+ if (!server_data->is_stopped)
+ BUG("cannot free ipc-server while running for '%s'",
+ server_data->buf_path.buf);
+
+ accept_thread_data = server_data->accept_thread;
+ if (accept_thread_data) {
+ if (accept_thread_data->fd_listen != -1) {
+ /*
+ * Only unlink the unix domain socket if we
+ * created it. That is, if another daemon
+ * process force-created a new socket at this
+ * path, and effectively steals our path
+ * (which prevents us from receiving any
+ * future clients), we don't want to do the
+ * same thing to them.
+ */
+ if (!socket_was_stolen(
+ accept_thread_data))
+ unlink(server_data->buf_path.buf);
+
+ close(accept_thread_data->fd_listen);
+ }
+ if (accept_thread_data->fd_send_shutdown != -1)
+ close(accept_thread_data->fd_send_shutdown);
+ if (accept_thread_data->fd_wait_shutdown != -1)
+ close(accept_thread_data->fd_wait_shutdown);
+
+ free(server_data->accept_thread);
+ }
+
+ while (server_data->worker_thread_list) {
+ struct ipc_worker_thread_data *wtd =
+ server_data->worker_thread_list;
+
+ server_data->worker_thread_list = wtd->next_thread;
+ free(wtd);
+ }
+
+ pthread_cond_destroy(&server_data->work_available_cond);
+ pthread_mutex_destroy(&server_data->work_available_mutex);
+
+ strbuf_release(&server_data->buf_path);
+
+ free(server_data->fifo_fds);
+ free(server_data);
+}
diff --git a/contrib/buildsystems/CMakeLists.txt b/contrib/buildsystems/CMakeLists.txt
index 4bd41054ee7..4c27a373414 100644
--- a/contrib/buildsystems/CMakeLists.txt
+++ b/contrib/buildsystems/CMakeLists.txt
@@ -248,6 +248,8 @@ endif()
if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
list(APPEND compat_SOURCES compat/simple-ipc/ipc-shared.c compat/simple-ipc/ipc-win32.c)
+else()
+ list(APPEND compat_SOURCES compat/simple-ipc/ipc-shared.c compat/simple-ipc/ipc-unix-socket.c)
endif()
set(EXE_EXTENSION ${CMAKE_EXECUTABLE_SUFFIX})
diff --git a/simple-ipc.h b/simple-ipc.h
index cd525e711bd..8a6dfc72c83 100644
--- a/simple-ipc.h
+++ b/simple-ipc.h
@@ -5,7 +5,7 @@
* See Documentation/technical/api-simple-ipc.txt
*/
-#if defined(GIT_WINDOWS_NATIVE)
+#if defined(GIT_WINDOWS_NATIVE) || !defined(NO_UNIX_SOCKETS)
#define SUPPORTS_SIMPLE_IPC
#endif
@@ -151,6 +151,11 @@ struct ipc_server_data;
struct ipc_server_opts
{
int nr_threads;
+
+ /*
+ * Disallow chdir() when creating a Unix domain socket.
+ */
+ unsigned int uds_disallow_chdir:1;
};
/*
--
gitgitgadget